Unicorn helmet



FIG. 1 is a front left perspective view of a unicorn helmet showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The evenly broken lines in the figures represent portions of the unicorn helmet that form no part of the claimed design. 

CLAIM I claim the ornamental design for a unicorn helmet, as shown and described. 